In severe earthquakes one of the greatest causes of damage is fire, aggravated by the rupturing of fuel lines and uncontrolled escape of readily combustible fuel. The invention relates to valves which may be inserted in such fuel lines, particularly adjacent the entrance of such lines into buildings and to earthquake-responsive mechanisms which will effect a closure of the valve when subjected to a predetermined minimum severity earthquake. Examples of earlier attempts to provide such mechanisms are disclosed in U.S. Pat. Nos. 2,054,563; s,158,753; 2,229,543; 2,615,461; and 2,873,753.